matching a text input with a hashed value in MySQL

I have a winform c# application. It connects to MySQL remotely and matches passwords stored in the MySQL database table . The passwords are stored using SHA1. I have stored a default value : "mypassword" and hashed it using SHA1.

When th开发者_开发百科e application runs, first the user is asked to enter the password. For this if i use the below mentioned function then it generates a different hash string when compared to the one generated by MySQL SHA1 function. How to match the values? Please help.

  public static string HashCode(string str)
        {
            string rethash = "";
            try
            {

                System.Security.Cryptography.SHA1 hash = System.Security.Cryptography.SHA1.Create();
                System.Text.ASCIIEncoding encoder = new System.Text.ASCIIEncoding();
                byte[] combined = encoder.GetBytes(str);
                hash.ComputeHash(combined);
                rethash = Convert.ToBase64String(hash.Hash);
            }
            catch (Exception ex)
            {
                string strerr = "Error in HashCode : " + ex.Message;
            }
            return rethash;
        }
    }

Am calling it like this :

 string hashedvalue =  HashCode("mypassword");
            MessageBox.Show("The hashed value is : " + hashedvalue);

Is hashing of both are different?

SHA-1 hash from MySQL is a hex-encoded string, while C# gives Base64-encoded string, so try this

rethash = BitConverter.ToString(hash.Hash).Replace("-", "");